The present invention relates to stringed musical instruments, particularly to guitars, and more specifically to guitar fretboards, including molded guitar fretboards and molded guitars.
Most stringed instruments comprise a fingerboard, which is typically a long strip of wood against which strings are pressed during play of the instrument. On many stringed instruments, such as guitars, the fingerboard, or fretboard, is fitted with small metal frets against which the strings are pressed so as to produce different musical notes in 1 increments when the strings are plucked or strummed.
In recent years, some portions of the process of guitar fretboard construction have become automated. However, there is still considerable time and effort required for fitting and assembling the various components of the fretboard, even though the components themselves may be produced in an automated manner.
A top view of a typical conventional fretboard 100 is shown in FIG. 1A. The fretboard 100 typically comprises a straight section of hardwood, often ebony or rosewood. A plurality of slots (not shown in the figure) are cut across the width of the fretboard into which are installed frets 110 (usually consisting of fretwire), which stand above the fretboard surface by about 0.030-0.045xe2x80x3. By pressing down on a guitar string between the frets at various positions on the fretboard, the user can produce different musical notes. A typical fretboard length 101 for a guitar is 19xe2x80x3. A first fretboard end width 102 for a fretboard length of 19xe2x80x3 is typically, 1.7xe2x80x3, whereas a second fretboard end width 103 for the same length fretboard is typically 2.1xe2x80x3.
The fretboard 100 forms a xe2x80x9cmusical note scalexe2x80x9d defined by a specific distance between each of the frets 110. This specific distance diminishes from left to right in FIG. 1A and requires that the frets must be spaced precise distances apart. The first fret on the left is located a distance (from the left end) of 1/17.8171 of the xe2x80x98scale lengthxe2x80x99, where the scale length is defined as the total length of the guitar string (typically 25xe2x80x3), set into oscillation. The second fret is set to the right of the first fret at a distance equal to 1/17.817 of the remaining distance (the scale length minus the first fret distance). This pattern of distance spacing continues for the remaining frets, typically 19-24 frets in total depending on the guitar.
The top of fretboard 100 is contoured with a curved or arched-shape, as shown in FIG. 1B, which illustrates an end view of the fretboard 100 of FIG. 1A. This shape is intentionally provided for the comfort of the user while forming bar chords, which require more finger pressure on the fretboard than open chords. A guitar that has its strings set low for ease of chording is termed to have a xe2x80x98low actionxe2x80x99 while strings that are set high and require greater pressure for chording are said to have a xe2x80x98high actionxe2x80x99. The radius of curvature used for fretboards typically varies from 7 to 16xe2x80x3, but a radius of 12 to 16xe2x80x3 may be chosen to suit the average user. A fretboard height 104 for a 19xe2x80x3 long fretboard as in FIG. 1 A is typically xc2xcxe2x80x3.
FIG. 1C illustrates a side view of a conventional neck and fretboard assembly. At each fret position on the fretboard 100, the fretwire must be cut to the correct width, and the -edges must be filed to a comfortable shape for a user""s hand and fingers. Finally, all of the frets 110 (typically 19 in total) may be filed or sanded to provide a horizontal surface that is level or straight prior to gluing the entire fretboard 100, including the frets 110, to guitar neck 120. Although specific tolerances for the xe2x80x9clevelxe2x80x9d of all the frets of a fretboard are seldom found in the prior art literature, the tolerances appear to range from approximately 0.005-0.010xe2x80x3 prior to tensioning the strings the guitar neck 120 may typically comprise a truss rod 130 (shown in dashed lines) inserted therethrough in a cavity along the length of the guitar neck 120 and typically in the center thereof, extending from headstock 140 past heel 150 into the guitar body. The first fretboard end width 102 (see FIG. 1A) is measured at an end of the fretboard located at nut 160, whereas second fretboard end width 103 (see FIG. 1A) is measured at another end of the fretboard located between the heel 150 and a bridge (not shown) over which the guitar strings are passed.
xe2x80x9cSteelxe2x80x9d fretwire is made of a hard nickel steel alloy, sometimes called xe2x80x9cnickel silverxe2x80x9d. Although the fretwire used in frets is subject to wear by constant string friction during usage, it can last several years before replacement is required. Fretwire replacement and alignment costs for an entire set of frets on a fretboard can be quite costly.
The requirement for high precision in fret construction and placement, together with the high cost of replacing worn frets are some drawbacks of the use of fretwire.
Several known arrangements exist which have attempted to overcome some of the drawbacks inherent with the installation of fretwire on a conventional wooden guitar fretboard. In one such arrangement, a fretboard and frets are machined with a computer milling machine. Such an arrangement, although able to produce a fretboard and frets with shapes and dimensions of high accuracy, is not well suited to the low-cost production of a fretboard and frets, thereby imposing a barrier with respect to its practical use. Other known arrangements employ the concept of having a molded fretboard (and/or molded guitar comprising that molded fretboard) having integral frets, thereby reducing concerns relating to the placement and preparation of frets at particular positions on the fretboard. Examples of patents making reference to a fretboard for a guitar, with the fretboard having integral frets, include: Canadian Patent 1,080,522 issued to Bond on Jul. 1, 1980; U.S. Pat. No. 5,072,643 issued to Murata on Dec. 17, 1991; U.S. Pat. No. 4,290,336 issued to Peavey on Sept. 22, 1981; and U.S. Pat. No. 5,033,351 issued to Nomura on Jul. 23, 1991.
However, there are still drawbacks relating to the above-listed patents. Although some known arrangements, such as those in the Bond patent, appear to discuss the concept of providing integral frets that have good wear characteristics as compared to steel frets, there is little indication as to how these characteristics are specifically obtained. There are references to the use of glass fibers in Murata and a glass-filled neck in Peavey. However, the purpose of the glass fibers, as described in Murata, is to provide strength, and not abrasion-resistance. Peavey does not specifically mention how frets are fabricated, what they are made of, or how they are integrated with the finger board.
The use of glass beads and resin in a musical instrument is taught in U.S. Pat. No. 5,911,168 issued to Enserink on Jun. 8, 1999. However, the glass beads as described in Enserink have a low density and are not used for the purpose of providing strength or preventing abrasion but for the purpose of decreasing overall weight. These glass beads would be buoyant and are not suitable for forming a surface layer on a fretboard. Additionally, the wall thickness of the glass beads is thin (1-3 microns) and is unlikely to provide adequate abrasion resistance, in that the bead wall would most likely collapse under any significant pressure exerted thereon.
Therefore, there is a need for a guitar fretboard that can overcome at least one of the drawbacks of the prior art arrangements.
The present invention provides a molded fretboard for use with a musical instrument, said fretboard having frets molded integrally herewith, said frets having abrasion resistant characteristics and being composed, in a working region thereof, of a molded mixture including glass beads and resin, said mixture having a higher proportion by volume of glass beads than of resin, and said glass beads being compacted such that each glass bead is in contact with at least one other glass bead.
In the molded fretboard of the present invention, the proportion of glass beads to resin is preferably in the range of about 60:40 to 70:30. Also, the molded fretboard is itself preferably composed substantially of a molding mixture including glass beads and resin, wherein the molding mixture has a higher proportion by volume of glass beads than of resin, whereby the top surface of the fretboard is provided with abrasion resistance.
The glass beads used in the molding mixture are preferably solid glass beads having a diameter in the range of about 1 to 500 microns, with a diameter in the range of about 30 to 150 microns being more preferable. The glass beads are preferably composed of a material selected from the group comprising sodalime, barium titanate, and borosilicate.
The resin used in the molding mixture is preferably composed of one or more materials selected from the group comprising encapsulating epoxy resin, polymer resin, polyester resin, amine-cured epoxy resin, brominated epoxy resin, epoxy novolac resin, bisphenol-A/F based resin, glycidal-based epoxy resin, water-based epoxy resin, casting resin, UV-cured resin, epoxy-polamide combination, and any combination thereof.
Another aspect of the present invention provides a stringed musical instrument comprising a molded fretboard having frets molded integrally therewith, said frets having abrasion resistant characteristics and being composed, in a working region thereof, of a molded mixture including glass beads and resin, said mixture having a higher proportion by volume of glass beads than of resin, and said glass beads being compacted such that each glass bead is in contact with at least one other glass bead.
A further aspect of the present invention provides a process for producing a molded fretboard for use with a stringed musical instrument, comprising the steps of a) pouring a pre-mixed molding mixture of glass beads and resin into a mold plate comprising fret grooves to permit said glass beads to settle into at least the working region of the fret such that each glass bead is in contact with at least one other glass bead, said mixture having a higher proportion by volume of glass beads than of resin; and b) curing the resin to produce a molded fretboard having abrasion resistant frets integrally formed thereon.
It is alternatively possible to perform the process of producing a molded fretboard for use with a stringed musical instrument as above wherein step a) is replaced by the following steps: a1) pouring a molding mixture of glass beads into a mold plate comprising fret grooves, thus creating a glass bead layer in at least the working region of the fret such that each glass bead is in contact with at least one other glass bead, said mixture having a higher proportion by volume of glass beads than of resin; a2) adding a layer of resin on top of the glass bead layer to form an initial thin layer of resin thereon; and a3) allowing the resin to permeate the glass bead layer, without disturbing the beads, so that the resin permeates throughout the entire bead volume including the fret grooves.
The process as defined above may further comprise the step of compressing the glass beads into the fret groove and reducing any air gaps within the fret surface, so as to increase the density per volume of glass beads.
A still further aspect of the present invention provides a method of ensuring the linearity of a fretboard/fingerboard on a stringed musical instrument comprising the steps of: removably attaching one or more linear steel edges to the upper surface of the fretboard to ensure the linearity of the fretboard, regardless of the curvature of the neck; adjusting, with a height adjusting means, the height of the fretboard relative to the neck; injecting an adhesive between the fretboard and the neck; and removing the steel edges once the adhesive is bound.
Another aspect of the present invention provides a method of ensuring the linearity of a neck of a stringed musical instrument comprising the steps of: removably attaching one or more linear steel edges to the upper surface of the fretboard to ensure the linearity of the fretboard; adjusting, with a height adjusting means, the height of the fretboard relative to the neck, to establish linearity of the neck; injecting an adhesive between the fretboard and the neck; and removing the steel edges once the adhesive is bound.
The present invention also provides a fabrication method for ease of manufacturing to be used in order to design a fretboard of unit body construction, including body and frets as one, using resins poured into molds. Such a process would reduce construction time (and costs) considerably and allow a more precise construction of a fretboard to a specific required design shape, which would result in improved playing action. The use of a mixture of resin (or composite resins) and glass beads for fret construction results in frets that have similar, and even better, xe2x80x98wearxe2x80x99 characteristics as compared to the conventional frets used in guitars which are constructed from steel fretwire and are slow to wear from abrasion.
The installation process taught herein comprises attaching the xe2x80x98straightxe2x80x99 fretboard after the neck curvature is set by tensioning of the strings. This method provides solutions to the problem of having a bowed neck and the problem of having a non-straight fretboard simultaneously. As such, a method according to the present invention may be used to ensure the linearity of a fretboard/fingerboard on a stringed musical instrument. A method according to the present invention may also be used to ensure the linearity of a neck of a stringed musical instrument after the strings are tensioned.